Nokea
Parents ask the nurse if there was something that should have been done during the pregnancy to prevent their childs cleft lip. Which statement should the nurse give as a response?
- A. This is a type of deformation and can sometimes be prevented.
- B. Studies show that taking folic acid during pregnancy can prevent this defect.
- C. This is a genetic disorder and has a 25% chance of happening with each pregnancy.
- D. The malformation occurs at approximately 5 weeks of gestation; there is no known way to prevent this.
Correct Answer: D
Rationale: Cleft lip, an example of a malformation, occurs at approximately 5 weeks of gestation when the developing embryo naturally has two clefts in the area. There is no known way to prevent this defect. Deformations are often caused by extrinsic mechanical forces on normally developing tissue. Club foot is an example of a deformation often caused by uterine constraint. Cleft lip is not a genetic disorder; the reasons for this occurring are still unknown. Taking folic acid during pregnancy can help to prevent neural tube disorders but not cleft lip defects.
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The nurse is teaching parents of a child with cri du chat syndrome about this disorder. The nurse understands parents understand the teaching if they make which statement?
- A. This disorder is very common.
- B. This is an autosomal recessive disorder.
- C. The crying pattern is abnormal and catlike.
- D. The child will always have a moon-shaped face.
Correct Answer: C
Rationale: Typical of this disease is a crying pattern that is abnormal and catlike. Cri du chat, or cats cry, syndrome is a rare (one in 50,000 live births) chromosome deletion syndrome, not autosomal recessive, resulting from loss of the small arm of chromosome 5. In early infancy this syndrome manifests with a typical but nondistinctive facial appearance, often a moon-shaped face with wide-spaced eyes (hypertelorism). As the child grows, this feature is progressively diluted, and by age 2 years, the child is indistinguishable from age-matched control participants.
Which is characteristic of X-linked recessive inheritance?
- A. There are no carriers.
- B. Affected individuals are principally males.
- C. Affected individuals are principally females.
- D. Affected individuals will always have affected parents.
Correct Answer: B
Rationale: In X-linked recessive disorders, the affected individuals are usually male. With recessive traits, usually two copies of the gene are needed to produce the effect. Because the male only has one X chromosome, the effect is visible with only one copy of the gene. Females are usually only carriers of X-linked recessive disorders. The X chromosome that does not have the recessive gene will produce the normal protein, so the woman will not show evidence of the disorder. The transmission is from mother to son. Usually the mother and father are unaffected.
Turner syndrome is suspected in an adolescent girl with short stature. What causes this?
- A. Absence of one of the X chromosomes
- B. Presence of an incomplete Y chromosome
- C. Precocious puberty in an otherwise healthy child
- D. Excess production of both androgens and estrogens
Correct Answer: A
Rationale: Turner syndrome is caused by an absence of one of the X chromosomes. Most girls who have this disorder have one X chromosome missing from all cells. No Y chromosome is present in individuals with Turner syndrome. These young women have 45 rather than 46 chromosomes.
Which genetic term refers to the transfer of all or part of a chromosome to a different chromosome after chromosome breakage?
- A. Trisomy
- B. Monosomy
- C. Translocation
- D. Nondisjunction
Correct Answer: C
Rationale: Translocation is the transfer of all or part of a chromosome to a different chromosome after chromosome breakage. It can be balanced, producing no phenotypic effects, or unbalanced, producing severe or lethal effects. Trisomy is an abnormal number of chromosomes caused by the presence of an extra chromosome, which is added to a given chromosome pair and results in a total of 47 chromosomes per cell. Monosomy is an abnormal number of chromosomes whereby the chromosome is represented by a single copy in a somatic cell. Nondisjunction is the failure of homologous chromosomes or chromatids to separate during mitosis or meiosis.
The inheritance of which is X-linked recessive?
- A. Hemophilia A
- B. Marfan syndrome
- C. Neurofibromatosis
- D. Fragile X syndrome
Correct Answer: A
Rationale: Hemophilia A is inherited as an X-linked recessive trait. Marfan syndrome and neurofibromatosis are inherited as autosomal dominant disorders. Fragile X is inherited as an X-linked trait.